1. Technical Field
Example embodiments relate to a flash memory system, for example, to a designing method of a flash translation layer thereof.
2. Description of Related Art
Generally, since a flash memory is capable of erasing data of a cell electrically and collectively, it is used for computers and memory cards. Recently, since usage of portable information devices such as mobile phones, personal digital assistants (PDAs), and digital cameras has increased, flash memory are being used as storage devices instead of hard disk drives (HDD). The above-mentioned portable information devices generally require storage devices of high capacity in order to perform various functions (for example, playing movies, playing high quality music, and so forth).
FIG. 1 is a block diagram illustrating a typical memory system. Referring to FIG. 1, a system 100 using a flash memory device 112 as a storage unit includes a memory card 110, a central processing unit (CPU) 120, and a random access memory (RAM) 130. Each of the above components is electrically connected to a system bus 140 for delivering data. The memory card 110 includes a flash controller 111 and the flash memory device 112. The flash controller 111 performs an interfacing operation between a host and the system 100.
The memory card 110 includes a non-volatile flash memory as a storage medium where large-capacity data can be stored. Also, the memory card 110 includes a flash controller 111 for interfacing between the flash memory 112 and a host. A role of the flash controller 111 is related to a flash translation layer (FTL).
The flash memory 112 can provide a fast read speed with a relatively low cost compared to other memory devices. However, an erase operation should be and is performed first before data is written into the flash memory 112. In addition, a data unit to be erased is greater in size than that to be written. This characteristic prevents the flash memory 112 from being used as a main memory. Additionally, if the flash memory 112 is used as an auxiliary memory device, the above-mentioned erasure characteristic is a factor that prevents a file system for a general HDD from being stored as is in the flash memory 112.
Accordingly, in order to conceal an erase operation of the flash memory 112, the FTL is used between a file system and a flash memory. The FTL, maps a logical address that the file system generates into a physical address of the flash memory 112 where an erase operation is performed during a write operation of the flash memory 112. The FTL uses an address mapping table to make address mapping fast. In general, an address mapping table is configured using a high speed SRAM. However, unlike the HDD, the flash memory 112 has a disadvantage that an overwrite operation is not possible on a physical block.